The unexceptional fires in Madagascar’s grasslands

The prehistoric dynamics of fire, vegetation, and humans in Madagascar are still not resolved, though one might get a different impression from the simplified narrative told to galvanise conservation action.  Clearly, humans visited, hunted, and eventually settled the island over the last several thousand years, and lit the vegetation on fire throughout.   But what kinds of fire, in what kind of vegetation, how often, and with what impact?  Charcoal and pollen in lake sediment cores and archaeological digs have informed most of our recent scientific understandings of fire history on the island.  Perhaps further answers and hypotheses can be found from innovative botanical, remote sensing, and modelling research being done in Africa.  Most striking perhaps – in the face of all the alarmist discourse about the menace des feux de brousse in Madagascar – is how unimpressive Madagascar’s fires appear in any remote sensing image that includes neighbouring Africa (this one is taken from Archibald et al. 2010 in the International Journal of Wildland Fire).

8 years of African fire satellite fire data

This shows that African environments, characterised by a long co-evolution of hominids with fires and vegetation, are more analogous to Madagascar, where humans were long absent, than typically admitted.  What kinds of inspiration can be found in African research?  For one, Sally Archibald and colleagues undertook a modelling study of the evolution of human-driven fire regimes in African savannas, published recently in the journal PNAS.  One of their results is that in open landscapes (which would have their equivalents in central and western Madagascar), the total area burnt was not very different whether lightning or humans were doing the burning.  What is radically different, however, is the season of burn – humans universally move fire into the dry season, as opposed to lightning strikes which are more of a wet season phenomenon (which doesn’t mean they don’t burn:  as I see here in Fiji, a week without rain is enough to allow grass to burn).

William Bond, in the Journal of Biogeography, uses botanic tools to argue that Madagascar’s grasslands are analogous to South African ones (and were present long before humans and their fires).  In his broader work, he investigates the evolution of C4 plants in grassy biomes and argues that grasslands are under-researched and poorly conserved (see Bond and Parr 2010).  For Madagascar, an ideological blinder that shapes how we ask questions about the fire-vegetation-human dynamics is the presumption that forest is more valuable, better, and more natural than grasslands – a topic I previously addressed in my book Isle of Fire.  An advantage for South African researchers like Archibald and Bond is an appreciation of savannas and grasslands as valuable and natural.   Perhaps this can be an inspiration for future studies in Madagascar.

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